Touch-sensitive systems utilize specialized surfaces to allow a user to interact with the system using touches. For example, a tablet computer display may include a touch surface to allow the user to interact and control the tablet. Touch surfaces may be implemented by measuring resistance changes in the surface when the surface is touched, by measuring capacitance changes in the surface when touched, by measuring acoustical changes in the surface when touched, etc. One type of touch surface is a multi-touch surface. A multi-touch surface is capable of resolving multiple points of contact with the surface at once. For instance, a user of a multi-touch device may use two fingers to rotate a display, to zoom in on a portion of the display, etc.
When an object that includes multiple touch points is placed on a multi-touch-capable surface, the touch-sensitive system is able to resolve the touch points to identify the object. This allows a user to utilize a touch-sensitive system for game play. For instance, a user may place a number of game pieces onto a surface of a touch-sensitive system, and the touch-sensitive system is capable of identifying the pieces for interactive game play. Typically, the game pieces will include a number of touch points that contact with the surface in a particular configuration that is unique. However, the game pieces are often mass-produced, which may result in duplicate configurations of touch points across a variety of different game pieces. In this case, a touch-sensitive system may be easily confused when configurations between different game pieces are duplicated.